Conventionally, there are various devices that include a sight line detection portion, which detects the sight line of a subject person, and exercise control on the basis of the detected sight line. A certain proposed device displays an array of cursors, which each show a character, on an input dialog screen of a personal computer. When a specific cursor is gazed at, the device determines that an instruction is issued to input the character associated with the cursor (referring to Patent Literature 1, for example).
Further, the configuration described in Patent Literature 1 sets a target at the center of each cursor and automatically corrects the sight line detection portion. More specifically, when the sight line detection portion estimates that a specific cursor is gazed at, the deviation between a position that is detected as the center of a sight line by the sight line detection portion and a central position (a target) of the specific cursor is regarded as a detection error of the sight line detection portion and applied to the correction. In the configuration described in Patent Literature 1, the sight line detection portion is formed by a sight line sensor detecting an eyeball rotation angle and a process performed on the eyeball rotation angle, and the deviation is reflected in correction data used during the process performed on the eyeball rotation angle. The detection error not only includes an error caused by the sight line detection portion, but also an error caused by eyeball movement peculiar to the subject person (this applies hereinafter).
The inventor of the present disclosure has found the following. The configuration described in Patent Literature 1 sets a target at the center of a cursor displayed on a predetermined portion of the input dialog screen. Therefore, when a screen has a pattern or array that is not initially imagined by a designer of the device, the target cannot be set in a proper manner. Further, the sight line detection portion may detect the sight line of the subject person even when the subject person is looking at the outside. In such an instance, too, it is preferred that the target be properly set.